Drying apparatus



Aug. .4, 1931.

J- B. WELCH DRYING APPARATUS Filed July 51, 1926' 3 Sheets-Sneet l lanai! mull! J. B. WELSH DRYING APPARATUS Filed July 31. 1926 I 3 Sheets-Sheet 2 "mill mill! 1 "HUM III! 4; 1931. J. a. WELGH DRYING- APPARATUS Filed July 31, 1926 3 Sheets-Sheet QM M $54? iEazeawor. M 6 M 04;

Patented Aug.

JOHN B. WELCH, OF NEW ORLEANS, LOUISIANA DRYING APPARATUS Application, filed. July 31,

This invention relates to a progressive dry kiln for drying lumber and other material.

One object of the invention is to provide a I progressive dry kiln having a novel heating system which is adapted to permit the temperatures in different sections of the kiln to be controlled in a simple and efiicient manner to maintain conditions within the kiln conducive to most favorable drying.

Another object of the invention is to provide a progressive dry kiln of novel and improved construction having a heating system by which it is rendered capable of use I in drying both soft and hard Woods.

A still further object is to provide a pro gressive drykiln with a novel and improved heating system, comprising a series of heating units capable of maintaining a temperaantially uniformly from the green end to the dry end of the kiln, while maintaining efiicient recirculation therein. 7

These and other features of'the invention ly defined in specification.

and 5 comprise a lines 4-4 of Fig. Figs.

on the 6 and 7 comprise a similar lines 6-6.0f Fig. 1 and 7-? of Fig. 2. In the kiln drying of lumber, it hasbeen will be hereinafter described and particularthe claims at the end of this ferred view taken found that in order to avoidsurface drying and the cracking, warping, splitting, etc.,

incident to it, the ,1

nitial heating of the green lumber should take place in air of suificiently high humi dity to accomplish this heating without appreciable evaporation of the moisture content of the lumber. after the lumber has been thoroughly and uniformly heated in this manner, it is usually moved through the kil cessive regions containi stantly diminishing hu 9 the moisture may be gradually and un Then,

n, remaining in sucng heated air of conmidity in order that iform- 1926. Serial No. 126,119.

ly evaporated from within and throughout the lumber.

In practice, the above described drying process is conveniently carried out in a progressive dry kiln, such as is illustrated in the drawings, having an elongated heating chamber 10 with openings 12 and 14 at the opposite ends thereof closed by doors 16 and 18. The green lumber is stacked on trucks v which are mounted on rails 20 and moved go through the opening 12 into the green end of the heating chamber 10, and then'moved progressively, step by step, through the heat-' ing chamber until they emerge from the dry end thereof through the opening 14.

In order that the air in the green end of the heating chamber may be maintained in a condition ofrelatively high humidity and that the lumber, in progressing through the kiln from the green end to the dry end, may 7:) encounter air of constantly diminishing humidity, it has been the practice to spray live steam into the heating chamber 10 from noz- I zles 22 located within the chamber.

- In progressive dry kilns of the Welch type, illustrated in the U. Patent to J. B. Welch No. 1,517,928, of December 2, 1924, provision is madefor circulating and recirculating the air within the kiln, and to. this end, in the illustrated apparatus air ducts 24 and 26 are so formed in the bottom of the heating chamber 10 throughout the length thereof. Fresh air is admitted tothe ducts 24and '26 through openings 28 and 30 formed therein, and is conducted through the ducts and discharged as at the dry end of the kiln through openings 32, 34thereinr The air ducts 24., 26, as also provided with by-passopenings 38, 40, near the green end of the kilnthrough which hot humid air is so by-passed as set forth in detail in the above mentioned WVelch Patent No. 1,517,928, to be carried along with the fresh air passing through the ducts and transferred to the dry end of the kiln. Recirculation is thus main- 05 tainedand in the illustrated apparatus the ducts 24, 26 are provided with an additional set of by-pass openings 42, 44 located at a sec tion of the kiln intermediate the dry and wet ends thereof. Recirculation through an adtions suitable for hard Wood kiln drying are not entirely suitable for tl edrying of. soft Wood or very green Wood.

Forthe efficient..dryingof,hard Woods, it

has been found desirable to maintaina'rela tively largedflierence ot. temperature between the green. .end and the ,dry end otthe kiln, whereasin dryingsoft Woods,- and par;

ticularly green soft wo.od, a mucn, (higher green end temperature is; required because. oi the excessive moisture. content otsuch .Woods, and in order to provide aprogressive kiln suitable for drying both kinds ofwoochand.

at the sametime, to maintain most efficient, recirculation, a novel .heatingwsystem isprovided.

Referring moreparticularly to the drawings for purposes of illustration, the. heating systemin the kiln maybe regarded as, dividedinto threesections, A, B andC, located in the dry. end, the intermediate portion and the green .end, respectively, of theYkiln. As

" shown in Figs. 4 and 5, the. section A ascomposed,. in the preferred form of fOl11,l1efl-t}1l1g coils 46, 47, 48 and 49 located s de by side he; neath the ra1ls20; the. sectionB coi'np r ses four heating coils 50, 51., 52 and 53; and the section C is composed of heating coils. 54 and 55.

In order to, accurately anddefinitely control the temperature conditions.within the. kiln, provision is made for controllingthe ten'iperatures in each of the section s.r l3 and C independently oftheothersections. In;

addition,lpro-vision-is made within the. sec-. tion A for. controlling the temperature of the heating coils 46. and 49 independently of coils 47 and -48 and also .for controllin flthe..

temperature .ofcoils47 and 48 independently of coils 46 and 49. Similarly, insectionB,

provision is made for controllingthetemperature of the coils 50 and 53 independently of coils51 and 52,: and for controlling the temperature of coils 51 and 52 independently of coils 50 and 53.

Tothese, ends. .the coils. 50, 51,52 and 53..

of section Aware provided with inlet headers 56,57,58 and 59- to which livesteam is [UlllllttQ-l through piping 60 from a supply pipe 61, a valve 623 being. provided; in the. piping 61 to.controlthe..steam,admitted to.

this section. In order to, controlthe. temperature inthe coils 46 and 49,- valves 63.

and 64 are provided by means of Which the supply of steam to the headers 56 and 59 may be regulated. Similarly, a valve 65 is provided .by means of which the supply of steam to the headers 57 and 58 may be controlled to regulate the temperature of the coils 47 and 48.

In order -to regulate theteniperatures of the coils 50, 51, 52 and 53, Which comprise the section B, in a similar manner, they are providedwith inlet-headers 66, 67, 68 and 69 to which live steam is admitted from the supply pipe 61 through a control valve 70 andpiping 7 1.. Valves 72 and 73 are provided to control the steam supply to headers 66- and 56.1 so; that the: temperature ofcoils 5O and.53,-may; b e regulated independently and a-valve 74 is-als provided tocontrol the; steainisupplyto headers 67fand 68. and regulate; the temperature of the coils .51 and 52 The coils-54.;and. 55,;comprising section. 0

are provided with inlet headers 75 and-76.

to which live steam mayibe admitted from the supply pipe/.161; through a; control .valve 77 andpiping- ;78--to regulatethe temperature otthese coils.

I Each of the coils; 46., .47, 48, 49, 50, 51, 52 53, 54 and. 5 5-is provided; with an outlet header, 88,, from which-.uthe condensate. discharges through check. valve In the dryingot very .green hard Woods, it sometimesdesirable to-have-even less hcat in the green endlofthe kiln than would. be furnished biynthe, afore-described systenu In such cases -.ithas been foind-that. the sup ply of steam" to,the .coils 54 and 55amay bje-I shut off entirely and that a suflicient .qi air. tity of-heatior, the initial heating of. the lumber inrthe (green end of 1 thGnkIlI-l Willi circu-late. into ,the green end. from ,the interior section of the kiln.

In the progressive kilns heretofore ,used,

there have usually occurred abrupt changes. in temperature between adj acentsections due to a .nuich greatericoncentration of piper in oneisection thaninthe other- In the present kiln thisdifiiculty.isflovercome byarranging the. heating coils ;-so,, that, the amount of pipe usedincreases.gra-duallyand substantially uniformly ifrom the green I end v to the dry-end, To this;enehgin.the section G, composed of coils 54 and 55,,there are, two layers; otpipe (Fig. 1); In the-next.

sectionB coin-posed-otcoils 50, 51 52 and 53,; there are; two layers in the, left-hand portion and ,four. layers in; the-right hand por-. tion, While .in the section .A comprising. coils 46, 47 48 and- 49i, there.i are,four layers in the left-hand. portion and sixdayers inathe remainder (Fig, ,2) i In addition, to further Ll-d111, the gradual increase in ,the, amount of Pip there e wgreaterjnumberioif.pipes in each layer, of sectiomB than i in (each. .layer.

of section .O, and, a greater number in each layer of A than in a layer of section B. In the above described arrangement of heating coils, the greatest Concentration of piping occurs in a relatively small section at the extreme dry end of the kiln, thus offsetting the tendency of this end of the kiln to be cooled and rendering this end the hottest portion'of the kiln. In addition, to aid in maintaining this high temperature at the dry end of the kiln, provision is made for heating any cold air which may leak into the dry end about the door 18. For this purpose a heating coil 92 is extended across the dry end of the kiln, beneath the rails 20, and between the end wall; of the kiln and a battle plate 94 also extending across the dry end of the kiln.

In the kiln drying of soft Woods which contain a large percentage of moisture, it is necessary to apply considerable heat to the wood at the green end of the kiln to overcome the latent heat of vaporization of this moisture. In order, therefore, to provide additional heatwhen drying soft woods, an additional heating section D is provided which live steam to the coils 96 and 98, they are provided with inlet headers 1 00 and 102 to which steam is admitted from the supply pipe 61 through a control valve 104 and piping 106. The coils 96 and 98 are also provided with separate outlet headers 110 from I which the condensate drains through check valves 114:.

s As shown in Fig. 1, the portions of the coils 96 and 98 which occupy the green end of the kiln, have in the illustrated form, four layers of pipe, while the remaining portions which are in the intermediate section have two layers. This arrangement provides a convenient means whereby additional heat is furnished at the green end of the kilnto compensate for the heat absorbed in overcoming the latent heat of vaporization of the moisture in the wood, and also tends to offset the cooling effect exerted on this end of the kiln by the end wall and door.

The arrangement of the coils of the sections A, B, C and D is such and they are so positioned that, when they are used in the drying of soft woods, the temperature withthe center of the kiln to the ducts 24 and 26 I i through the openings 38, 40, 42 and 44:. In addition, the coils 50 and 52 are so positioned as to provide spaces between the coils and the side walls of the kiln through which the air has free access to the ducts through the outer portions of the openings 38 and 40.

While it is preferred to use the invention in the form disclosed, it will be readily understood that it may be embodied in other forms within the scope of the following claims.

Having thus described the invention, what is claimed is 1. In a progressive dry kiln,an elongated heating chamber, means for causing recirculation of the air within said chamber, means for progressively increasing the temperature within said chamber from the green end to the dry end thereof, and means for heating cold air which may leak into the dry end of In testimony whereof Ihave signed my name to this specification.

JOHN B. WELGH.

in the kiln increases substantially uniformly from the green end to the dry end. Also the coils are so arranged that they do not interfere with the circulation of air in the kiln. To this end, the coils 96 and 98 are spaced apart to allow the air free access in 

